fix(settings): use the host's @deepseek-ai/schemastery so volatile prefs apply

Every side-card switch was dead: settings.update returned OK and
cordis.patch.yml was written, yet the running plugin never saw the new value
and nothing reported an error.

Root cause: the plugin declared Config with the plain npm `schemastery`
(3.18.0), which has no volatile support. The host resolves plugin config via
`runtime.Config['~standard'].validate()` — i.e. the plugin's OWN schemastery —
so `meta.volatile` nodes were never wrapped in cosmokit volatile references.
`cordis-plugin-loader`'s `_commitVolatile()` bails out as soon as
`volatileEntries(fiber.config)` is empty, so every volatile-only edit was
silently dropped: no in-place update, no plugin restart.

Fix: import z from '@deepseek-ai/schemastery' (peer provided by the host at
mount; pinned 3.18.4 as a devDependency for the dev tree), matching the
repo's existing pnpm-workspace convention for @deepseek-ai/* peers.

Verified: probe reports tabsIsVolatile=true and revision climbing 0->6 across
six writes, each read-back matching the written value (previously the value
was frozen and revision stuck at 1).

Also in this change:
- apes tab ids lose their colon (apes:tasks -> apesTasks, ...): the host's
  settings projection dropped map keys containing a colon.
- sidebar prefs ns follows the profile entry id (`better-sidebar`).
- subagent rows degrade to summary rows when the root catalog never hydrates.
- docs/feedback-0.2.0-rc2-contract-gaps.md: four host contract gaps, gap 4
  documenting the silent volatile-write drop above.

Gates: typecheck 0, lint 0, build 0, test 131 files / 1385 passed.

tests/plugin-shape.spec.ts

@@ -53,7 +53,7 @@ describe('dsh-apes-sidebar plugin export shape', () => {
 
   it('registers the side card preferences schema with the documented defaults', async () => {
     const { PrefsSchema, SIDEBAR_PREFS_NS, SIDEBAR_PREFS_DEFAULTS } = await import('../src/config.ts')
-    expect(SIDEBAR_PREFS_NS).toBe('dsh-apes-sidebar')
+    expect(SIDEBAR_PREFS_NS).toBe('better-sidebar')
     const resolved = (PrefsSchema as unknown as {
       (input: Record<string, unknown> | undefined): Record<string, unknown>
     })(undefined)